Fault-Tolerant Control Using ℌ∞ Sliding Mode Observer

A fault-tolerant control scheme for a class of nonlinear systems subject to actuator faults and system disturbances is proposed and analyzed. Fault and state estimates are generated by an H_∞ sliding mode observer, making them more robust to disturbances. They are used to form an output feedback controller that suppresses the effects of faults and disturbances, resulting in an integrated fault tolerant control design. Stability of the closed loop system is proved using Lyapunov analysis. The integrated fault tolerant control design is applied to a permanent magnet synchronous motor. Simulation results demonstrate that with the enhanced robustness of the state and fault estimates to disturbances, the proposed controller produces significantly improved closed loop performance.